The goal of plant breeding is to combine various desirable traits in a single variety/hybrid. Such desirable traits may include any trait deemed beneficial by a grower and/or consumer, including desirable flower color or pattern, resistance to insects or disease and tolerance to environmental stress.
Breeding techniques take advantage of a plant's method of pollination. There are two general methods of pollination: a plant self-pollinates if pollen from one flower is transferred to the same or another flower of the same plant or plant variety. A plant cross-pollinates if pollen comes to it from a flower of a different plant variety.
Plants that have been self-pollinated and selected for type over many generations become homozygous at almost all gene loci and produce a uniform population of true breeding progeny, a homozygous plant. A cross between two such homozygous plants of different genotypes produces a uniform population of hybrid plants that are heterozygous for many gene loci.
Conversely, a cross of two plants each heterozygous at a number of loci produces a population of hybrid plants that differ genetically and are not uniform. The resulting non-uniformity makes performance unpredictable.
The Tagetes genus is a member of the family Asteraceae, alternatively known as Compositae, and comprises around thirty species of strongly scented annual or perennial herbs.
Tagetes are native from Arizona and New Mexico to Argentina. Cultivated genera include Tagetes erecta commonly referred to as African marigold, Tagetes patula or the French marigold, Tagetes erecta x patula also known as the triploid marigolds, and Tagetes tenuifolia also known as Tagetes signata or commonly signet marigold. Of the cultivated marigolds, the French marigolds are especially valued in the landscape as a colorful upright-mounding border plant. Cultivated marigolds perform well in dry or moist conditions with strong-scented, showy flowers that are excellent in borders and as cut flowers. They produce a long-term display of colors, which include yellow, orange, and gold with shades of red and maroon from the triploids and French types. Flowers range in size from 2.5 cm for the French varieties to as broad a 13 cm for some of the African varieties. Plants range from 15 cm in height to 91 cm and fill in well in the garden.